Removable spacing die for casting rotors with ventilating ducts



April 18, 1950 v E. c. GEORGE 2,504,824

REMOVABLE SPACING DIE FOR. CASTING ROTORS WITH'VENTILATING DUCTS Filed March 27, 1948 x 4 0 0 /3 a O Q r a 7 Q G W U U E W y 5 .5 /vW/ M 0329.2 go ch54 fig;v g I SM/g Patented Apr. 18, 1950 REMOVABLE SPACiNG DIE FORCASTI'NG ROTORS WITH VENTILATING DUCTS Edgar 0. George, Cincinnati, Ohio, assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis, a corporation of Delaware Application March 2'1, 1948, Serial No. 17,408

7 Claims. 1

This invention relates generally to improvements in the manufacture of electric motors and refers particularly to ventilated squirrel cage rotors of the cast type now common in the art and to methods of making the same.

It is an object of this invention to provide a method of forming a radial ventilating passage in a rotor through the use of areusable temporary spacer between groups of laminations, the spacer being made of any suitable material that is readily removable without destruction from the rotor after casting the rotor conductors.

It is also an object of this invention to maintain groups of rotor laminations permanently spaced after casting by the formation of spacing means which remain when the reusable temporary spacer is removed.

The objects of the invention are preferably attained by the use of a spacer comprising a plurality of removable dies closely and radially disposed between two groups of core laminations, so that the openings formed between adjacent dies align with the conductor bar slots of the laminations.

The novel features that I consider characteristic of this invention are set forth with particularity in the appended claims. The invention itself, together with additional objects and ad- 2 helical to cause the slots of the stacked laminations to align with skew.

To provide one or more radial ventilating ducts in the finished rotor at least one temporary spacer is inserted between groups of the laminations 8. Such a temporary spacer comprises a plurality of removable dies I! each of which may section, either L-shaped or T-shaped, and each vantages thereof, will be best understood from r the following description of a specific embodiment when read in connection with the accompanying drawings in which:

Fig. 1 is an oblique view of the assembled laminations and of a temporary spacer comprising a plurality of substantially L-shaped'removable dies for a die cast rotor showing parts thereof broken away;

Fig. 2 is an enlarged view inelevation of one of the removable dies shown in Fig. 1;

Fig. 3 is a view in side elevation of the die shown in Fig. 2;

Fig. 4 is a view in elevation of a modified removable die of substantially T-shape; and

Fig. 5 is a view in side elevation of the die shown in Fig. 4.

Referring now particularly to the accompanying drawings, the numeral 8 designates the rotor core laminations which are made from thin .sheets of steel of a suitable grade. These laminations 8 are punched to provide conductor bar slots 9, and a bore l0 having a keyway II for reception of a spider mounted on a rotor shaft.

For casting the rotor conductors the,laminations 8 are stacked on a mandrel I2 having a keyway I3 and are aligned with each other by means of a key It fitted in the keyways of the laminations and of the mandrel.

The keyways may be parallel to the mandrel axis so that the slots of the stacked laminations align without skew, or the keyways may be die is tapered along its length away from the end having the projection. With respect to the axis of the mandrel or the circle about which they are disposed, the diesare radially and axially tapered.

The enlarged views of the dies shown in elevation in Figs. 2 through 5 more clearly illusa plane or curved, and may be parallel or inclined toward each other to afford a draft for removing the die after casting the conductor bars. Surfaces 21 and 28 indicate a further inclination of the sides near the lower end of the die and are the surfaces of abutment of adjacent dies radially arranged as in Fig. 1.

T-shaped die 23 may be tapered similarly to die l1; surfaces 32 and 31 may be plane or curved, and may be parallel or inclined toward each other; the side surfaces of the projections of the die may be parallel as are surfaces 34, 35, and may be inclined as are surfaces 33, 36. The latter surfaces of adjacent dies will be in abutment when the dies are radially disposed as in Fig. 1.

The front surface 25 and the back surface 3| of die H, as well as surfaces 38, 39 of die 23, may form parallel planes, or planes inclined inward toward the lower end, giving an axial taper to each die to facilitate the removal of the dies molten metal that is to form the conductor bars.

The dies may be so tapered that the so-called points of abutment of adjacent dies are actually surfaces of contact lying substantially in radial planes. 7

The thickness of the dies of a spacer depends on the desired size of the radial ventilating duct. If the dies extend inward to the mandrel, one of the diesmay be shortened or notched to accommodate the key II. For a rotor comprising a spider for providing longitudinal ventilating passages to be connected with a radial ventilating duct, the dies may be disposed about a circle of a diameter somewhat larger than the inner diameter of the laminations so that none ofthe connections between the longitudinal passages and the radial duct will be blocked by an arm of the spider.

The dies H are so constructed and arranged that the openings 20 between adjacent dies cooperate with the conductor bar slots of the adjacent laminations to form a mold for casting the conductor bars in the aligned slots and spacer openings. These openings 20 may be of the same size and configuration as the conductor bar slots, or they may be larger than the slots, as illustrated in Fig. 1, so as to form enlargements of the conductor bars upon casting.

The core laminations are assembled with at least one spacer interposed between groups of the laminations and thelaminations are firmly clamped together, binding the removable dies disposed between two laminations to maintain the spacer openings 20 aligned with the conductor bar slots 9. Thereafter the conductor bars are cast in the slots of the laminations in any suitable known manner, the molten metal filling all of the slots 9 and all of the openings 20 of the spacer. The enlargements of the conductor bars in the temporary spacer form permanent spacers between the groups of laminations.

After casting the conductor bars the dies forming the temporary sparer'may be removed. The vacated space then left between the adjacent laminations is the radial ventilating duct 24 which surrounds the conductor bars. The conductor bars in the radial ventilating duct have a cross sectional shape determined by the spacer mold, the shape of openings 20, and may be substantially triangular or wedge shaped, so the conductor bars eifectively act as fans in the ventilating duct. I

The spacermay extend beyond the outer periphery of the laminations, as illustrated, or may extend only to the outer periphery. Such an ex tension of the spacer beyond the periphery of the laminations is for aiding in removal of the dies forming the spacer. The outer portion of each die may have an opening i8 for attaching a tool for loosening and removing each die.

The opening l8 may be replaced by a notch in at least one of the faces of the die. The tool for removing the die may comprise a bar provided at one end with a hook to be inserted in the open ing of the die, and at the otherend with an enlargement. An annular hammer sliding on the bar is used for applying impacts to the enlarged end of the bar to loosen the die away from the cast material and from the tightly stacked but somewhat resilient laminations.

When the dies do not extend beyond the periphery of the laminations, they may be provided with radial tapped holes for the insertion of bolts to be used for removing the dies from the laminations.

. passages connecting with the radial ventilating passages. The same result can be achieved by means .of a splined shaft forming ventilating ducts, or by using laminations punched to provide longitudinal ventilating passages and mounting ,the 'core directly on the rotor shaft.

From the foregoing description'taken in connection with the accompanying drawings, it will be readily apparent to those skilled in the art that this invention provides a temporary spacer that can be economically produced for repeated use as well as an improved method of providing squirrel cage rotors with radial ventilating passages.

It is claimed and desired to secure by Letters Patent:

1. A temporary spacer for forming a radial ventilating duct between adjacent laminations in a laminated squirrel cage rotor to be provided with cast conductor bars embedded in aligned slots in annular laminations of predetermined inner and outer diameters, said spacer consisting of a plurality of removable dies of substantially rectangular cross section disposed between said adjacent laminations, each die having a projection on one side at one end, said side and the opposite side of each diebeing tapered from said end, said dies being closely, uniformly and radially arranged with said ends outward about a circle of a diam eter not less than the inner diameter of said laminations and having a portion of each said projection extending beyond a circle of a diameter equal to the outer diameter of said laminations, adjacent dies having surfaces abutting at each end but spaced apart intermediate the ends to form openings therebetween so as to align with said slots, said surfaces being within the area between said circles to cooperate with said slots so said dies and said adjacent laminations form moldsfor said conductor bars. said outer portions of said projections defining means for attaching a tool for removing said dies. the sides of said dies in contact with said laminations tapering to facilitate the removal of said dies without damage to said dies.

2. A temporary spacer for forming a radial ventilating duct between adjacent laminations in a laminated squirrel cage rotor to be provided with conductorbars cast in aligned slots in annular laminations of predetermined inner and outer diameters, said spacer comprising a plurality of removable dies of substantially rectangular cross section-disposed between said adjacent laminations, said dies being closely, uniformly and radially arranged about a circle of a diameter not less than the inner diameter of said laminations and having portions extending beyond a circle of diameter equal to the outer diameter of said laminations; adjacent dies abutting near both ends but spaced apart intermediate the ends to form openings therebetween so as to align with said slots, but being larger than said slots, and said abutments being within the area between said circles to cooperate with said slots so said dies and said adjacent laminations form molds for said conductor bars, the sides of said dies in contact with said laminations tapering to facilitate the removal of said dies.

3. A temporary spacer for forming a ventilating nated squirrel cage rotor to be provided with conductor bars cast in alignedslots in annular laminations of predetermined inner and outer diameters, said spacer comprising a plurality of removable dies of substantially rectangular cross section disposed between said adjacent laminations, each die having a projection on one side at one end, said side and the opposite side of each die being tapered from said end, said dies being closely, uniformly and radially arranged between two of said laminations with said ends outward, about a circle of a diameter not less than the inner diameter of said laminations, and extending outward beyond a circle of a diameter equal to the outer diameter of said laminations; said sides of adjacent dies abutting at points near both ends but spaced apart intermediate the ends v to form openings therebetween so as to align with said slots, but being larger than said slots, and said points of abutment being within the area between said circles to cooperate with said slots so said dies and said laminations form molds for said conductor bars, the sides of said dies in contact with said laminations tapering to facilitate the removal of said dies without damage to said dies.

a. A temporary spacer for forming a ventilating duct between adjacent laminations in a laminated squirrel cage rotor to be provided with conductor bars cast in aligned slots of annular laminations of predetermined inner and outer diameters, said spacer comprising a plurality of removable, dies of substantially rectangular cross section disposed between said adjacent lamination, each die having projections on opposite sides at one end, said sides being tapered from said end; said dies being closely, uniformly and radially arranged between two of said laminations, with said ends outward, about a circle of a diameter not less than the inner diameter of i said laminations, and'extending outward beyond a circle of a diameter equal to the outer diamduct between adjacent laminations in a iamislots, and said points of abutment being within the area between said circles to cooperate with said slots so said dies and said adjacent laminations form molds for said conductor bars, the sides of said dies in contact with said laminations tapering to facilitate the removal of said dies without damage to said dies.

6. A temporary spacer for forming a radial ventilating duct between adjacent laminations in a laminated squirrel cage rotor to be provided with conductor bars cast in aligned, slots in annular laminations of predetermined inner and outer diameters, said spacer comprising a plurality of removable dies of substantially rectangular cross section disposed between said adja cent laminations, each die having all four sides tapered from said end, said dies being closely, uniformly and radially arranged, with said ends outward, about a circle of a diameter not less than the innerdiameter of said laminations, and

extending outward at least to a circle of a diameter equal to the outer diameter of said laminations, adjacent dies abutting near both ends but spaced apart intermediate both ends to form openings therebetween so' as to align with said slots, and said abutments being within the area between said circles to cooperate with said slots so said dies and said adjacent laminations form molds for said conductor bars, said tapering or said sides of said dies in contact with said laminations facilitating the removal of said dies after said conductor bars have been cast.

7. A temporary spacer for forming a radial ventilating duct between adjacent laminations in a laminated squirrel cage rotor to be provided with cast conductor bars embedded in aligned slots in annular laminations of predetermined H inner and outer diameters, said spacer consisteter of said laminations; said sides of adjacent dies abutting at points near both end but spaced apart intermediate the ends to form openings therebetween so as to align with said slots, but

being larger than said slots, and said points 01' abutment being within the area between said circles to cooperate with said slots so said dies and said adjacent laminations form molds for said conductor bars, the sides of said dies in contact with said laminations tapering to facilitate gliie removal of said dies without damage to said es. I

5. A temporary spacer for forming a ventilating duct between adjacent laminations in a laminated squirrel cage rotor to be provided with conductor bars cast in aligned slots of annular laminations of predetermined inner and outer diameters, said spacer comprising a plurality of removable dies of substantially rectangular cross sectiondisposed between said adjacent laminations, each die having projections on cpposite sides at one end, said opposite sides being tapered from said end, said dies being closely, uniformly and radially arranged between two of said laminations, with said ends outward, about a circle of a diameter not less than the inner diameter of said laminations, and extending outward beyond a circle of a diameter equal to the outer diameter of said laminations: said sides of adjacent dies abutting at points near both ends butspacedapartintermediatethecndstoform openings so as to flisn with said ing of a plurality of removable dies of substantially rectangular cross section disposed between said adjacent laminations, each die having a projection on one side at one end, said side and the opposite side of each die being radially tapered from said end, said dies with said ends outward being closely, uniformly and radially arranged about a circle of a diameter not less than the inner diameter of said laminations, having a portion of said projection extending beyond a circle of a diameter equal to the outer diameter of said laminations, and adjacent dies abutting at each end but spaced apart intermediate the ends to form openings therebetween so as to align with said slots, said abutments being within the area between said circles to cooperate with said slots so said dies and said adjacent laminations form molds for said conductor bars, the sides of said dies in contact with said laminations tapering to facilitate the removal of said dies. EDGAR C. GEORGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

